Arundel Wildfowl and Wetlands Trust is just down the road from Arundel Castle in West Sussex.
There is charge for entering the site if you are not a WWT member. On the day I visited it was £11.50 for an adult.
The a large number of excellent hides and viewing areas, and the layout means you can get fairly close to the wildfowl there. A reasonably long lens 200-300mm would be advised generally, and longer in some of the hides overlooking the larger waters.
During the warmer months butterflies and insects will also be about so a bit of macro photography can be done then.
The trusts website also handily lists on its website what places / hides are best for photographing the different species of wildfowl and wildlife.
Please note
Photography is permitted on site providing it is for personal use only. All commercial/stock library photography must be agreed in advance with the centre and is subject to a fee.
OS Map Reference : TQ 02057 08068